💬 Battery Powered Sensors

  • Mod

    @Sebex I have never tried to run a Nano on battery, so I don't know but that looks like a regulator.

    The Nano operates at 5V and consumes much more power than a 3.3V Pro Mini.

    Yes, the regulator will consume power if it is not disconnected.

  • Hardware Contributor

    The big chip to the left is also a serial-usb converter which needs to be removed, making it not possible to program from the usb socket. Along with these components there are resistors and other components that might blead current so i dont think its that easy compared to just doing it to a Pro Mini.

  • Ok thnx guys, guess I'll be ordering a pro mini very soon!

  • Hardware Contributor

    @Sebex - i think thats the easiest way, but sometimes its fun to try to create something new - its not impossible, but I would try to reverse engineer the nano (already done - search arduino nano schematic) and there you have to identify all "not essential" components and remove those (ie, making it a big pro-mini) to be able to get the current down as much as possible.

  • @Sebex said in 💬 Battery Powered Sensors:

    A bit off topic maybe, but I was wondering how the 'pros' around here make the sensor small and sturdy for Arduino's with Si7021+ 2xAA battery pack. My DuPont wires seem a bit loose, so I'm wondering whether I should solder them. And perhaps someone 3d printed a case for an Arduino+Batterypack or some sorts.

    You may want to try wire wrapping. It’s faster than soldering, sturdier than DuPont and you can connect multiple wires on same pin. Works wonders for gnd and vcc. Of course if the project is yanked harder, the wire wraps come out.
    I made this small video for my home automation group in India. - hence prices for the wire wraps and tool are mentioned in local currency. I leant about this amazing technique from Andreas Spiess
    my video
    guy with Swiss accent

  • @Puneit-Thukral Both DuPont and wirewrap are generally considered as prototyping methods. For final device build and production more secure connections should be implemented.

  • @skywatch Agree with every word of yours. Not justifying myself here but wirewraps are deployed all over my house. I pour some hot glue to ensure that they don’t come loose. And then a 3D printed enclosure takes care of the elements.
    Also, it helps me to quickly repurpose the hardware.
    It’s just another approach.
    In an ideal world - where PCB shipments never arrive from China and locally they are a but expensive , this is my poor man’s alternative. 90F6D2B8-A1BA-4156-A23E-B7783A89FA49.jpeg 97A8362E-7B49-433F-8709-42E49469B161.jpeg Example photos. The coin cell holder is diy. Used shaving blades and wrapped wires and taped to create a circuit.

  • @Puneit-Thukral I understand 'poor mans alternative' soooo well! 😉

    Glue on the wirewraps will help keep them in place and mitigate thermal stress to some degree and also stop dust and moisture. But over time the glue will change and shrink/crack and things will start to become strange with that arrangement.

    It's hard to beat a good soldered joint in the end, that's why all the commercial kit is done that way.

    Nice case BTW. I also am working on 3D printed cases for some nodes. Another 6 weeks of lockdown and I should have started on them! 😉

  • @Puneit-Thukral interesting! Seems as a better option than Dupont, I'm gonna look into it.
    You mention hot glueing the wires yourself as extra protection. But I imagine you can also put a layer of solder on it right?

  • @Sebex yes, of course. I have done that as well. In case I need to repurpose something , removing solder completely away is a tougher job for me than peeling away a layer of glue. Guess, I am just lazy. 😃

  • @Puneit-Thukral haha okay I see.

    Another question, your case that you use in the video snaps onto the pins perfectly it seems. Did you 3d print that yourself? I'm looking to 3D print a case for my pro mini and some other sensors that snaps in a similar way so that nothing moves around. However I'd rather copy a proven design than figuring out the tolerances myself.

  • @Sebex Yes, I 3D printed on my ender 3 and I am using this on nodemcu running ESPhome. But I did not design it. Here is the Thingiverse link to it.
    Nodemcu case

    I would love to do similar case and a larger case like this to fit other boards. Its rock solid. I do not have skills to make a linear pattern like this. I think I should figure out how to do it.

  • @Puneit-Thukral cool, from what I read the pins are the same size as on Arduino's. I'll use this design to create one for myself.

  • @Sebex Do share the STL - it will be great and if you use Fusion360, then may I request for the F3D file.. I am semi-skilled when it comes to designing

  • @Puneit-Thukral Will do!
    After closer inspection the pins of the NodeMCU seem to be a lot bigger in size. However I am struggling to find the correct sizing of Arduino Pro Mini pins (width/thickness). The spacing between pins and length of them are easy to find but I cannot find the thickness at all. Do you have an idea?

  • @Sebex Will this help
    and should we move this conversation to another topic /PM as this is not relevant to this thread.

  • @mfalkvidd, on the image I see the following marking in red

    VCC ==> N/C

    Do you know what the meaning is?
    This VCC pin and the other VCC pin at the bottom of the image are connected. I verified with the multimeter.
    So, what's the purpose of this remark?

    These pins at the right are used to program the pro mini. I had no problems to program after removing the led and the power regulator. The programmer used the VCC to power the pro mini without any problem...

  • @evb I believe that the reason is to physically (and electrically) isolate the voltage regulator from the circuit. Then only VCC will work and not RAW.

    Essentially the same as removing the led or it's series resistor (only one or the other will do) and the regulator from the board.

  • @skywatch, you mean that in normal conditions with the power regulator, we connect the power supply (max 16VDC) to the raw pin and can take 3.3V or 5V, depending on which version, at the pin VCC?
    And that now it isn't possible anymore with the regulator removed?

    I would propose to change the picture :

    • there are 2 VCC pins, so the current picture is confusing
    • adapt the drawing and mention to connect the battery (2xAA) 3V directly to VCC pin at the bottom (not the VCC pin in the programming row of contacts!)

    @skywatch and @mfalkvidd, what do you think?

  • @evb said in 💬 Battery Powered Sensors:

    @skywatch, you mean that in normal conditions with the power regulator, we connect the power supply (max 16VDC) to the raw pin and can take 3.3V or 5V, depending on which version, at the pin VCC?
    And that now it isn't possible anymore with the regulator removed?

    Yes, because the regulator will drain batteries faster using raw than connecting an appropriate voltage to VCC....

    I would propose to change the picture :

    • there are 2 VCC pins, so the current picture is confusing
    • adapt the drawing and mention to connect the battery (2xAA) 3V directly to VCC pin at the bottom (not the VCC pin in the programming row of contacts!)

    @skywatch and @mfalkvidd, what do you think?

    I think it is up to the user to decide what pins they want to connect to and why.

  • Mod

    @evb I don't know what the N/C text means. Presumably N/C stands for Not Connected, but I don't understand what isn't (or shouldn't?) be connected, so I can't say anything about that part unfortunately.

    The device can be powered through any of the two Vcc pins. Use the one that is most convenient.

    I am not aware of any Arduinos that can handle 16V input on the raw pin. Most clones don't even handle 12V.

    If the regulator is removed, the Arduino can no longer be powered through the raw pin.

  • @mfalkvidd That's why I propose to adapt the article and image 🙂

    If even experienced people like you don't know what it means, what should beginners think?
    I was confused and did some extra research on schematics, etc on the internet and measurements on my pro mini, afraid to blow up my only TTL to USB programmer after the modification of the pro mini for saving power consumption 😓

    The 16V was found on a schematics from the arduino.cc (https://www.arduino.cc/en/uploads/Main/Arduino-Pro-Mini-schematic.pdf). I use typically a 9V power adapter to be safe.

    @skywatch You are right that the user finally decides what VCC pins he or she will connect, but we can help him and give a hint : if he uses the right VCC pin to solder his battery wire, he will have a hard time to connect his TTL to USB programmer...

  • Mod

    @evb yes I see your point. But changing things without understanding the background is troublesome, in my experience. Whoever created the original image probably had a good reason to write the N/C part. Therefore, I would prefer if any of the "Ancients" (i.e. people who joined the project before me) could chip in.

  • @evb MySensors is a a technical project that involves both hardware, software and firmare. It is not that easy for everyone to follow a single example and then get all that they want.

    Think of it as a leanring curve. You already found something that is not the way you want it to be for your use. Many others will agree with that. Some want it a different way.

    The main objective is to learn all you can (or need) to get your projects to where you want them. Some out there won't have a single battery node at all, some will be more advanced in battery power conservation than the case in this thread.

    I flagged a faulty 'build' example more than 2 years ago, but it is still there and still wrong. But mine works as it should because I studied the data sheets and did it the right way. Change does not come quickly it seems.

    You have to put time and a lot of effort into this unless you already work in such an area or have a degree in associated methodolgy.

  • @skywatch unfortunately, that is also the impression I have, the documentation is not always up to date and it is a laborious process to get it improved. 😞

    MySensors is a great project, but the learning curve is not negligible. Making it easier for beginners with real-world examples might make that learning curve a bit easier.

    I've already mentioned it, but one example is the workflow of the open source project Home Assistant. The setup of the documentation and the possible pull requests for improvement are easier to get accepted.

    If @mfalkvidd now manages to find and to wake up the 'Ancients', this article might be able to be improved anyway 😀 👍

  • Hardware Contributor

    @mfalkvidd Don't know if I'm qualified, but I've vague memory (or a wild guess). I think there were some pro-mini models that lost connection to one vcc-pin if you made the cut after the voltage regulator. And btw I never really know why the cutting method was so popular.

  • @m26872, your memory is correct. There are or were pro-mini models who lost connection on the VCC pin at the right if you removed the power regulator. (https://forum.pimatic.org/topic/383/tips-battery-powered-sensors/2).

    My batch of chinese pro mini's are not loosing their connection with the VCC pin at the right.

    @mfalkvidd, you can maybe adapt the wiki article with this extra info?

  • Meanwhile I found following forum topic : https://forum.mysensors.org/topic/2067/my-slim-2aa-battery-node. Thanks @m26872 🙂

    @mfalkvidd, I insist 😉 , if modifying these 'official' site articles turns out to be so difficult, can't a new section not be added like for example 'User experiences' or 'Advanced use' or 'Real world examples' or ... ?
    Now we are obliged to read through hours of forum topics, hoping to find more information somewhere.
    On one hand, this is of course instructive, but on the other hand it also wastes a lot of time looking for answers.
    If we already had a starting list of some topics from experienced users, the learning curve would already be smaller.

    I started my battery crusade months ago by ordering some Arduino Pro Mini's from our Chinese supplier AliExpress following the official site article.
    Because I could not obtain the given consumption of current, I began to search further.
    Today after hours of searching and reading on the forum, I realize that this choice was actually not the right one.
    I probably had better ordered the custom PCB from @m26872 and used a barebone 328P, or a Moteino or a Canique or...

    As far as the current of my pro mini is concerned, I'm stuck at a minimum of 133µA.

    • pro mini without power led and power regulator
    • refused using the MiniCore packet to 1.8V BOD and 1MHz internal
      • board : ATmega328
      • clock : internal 1 MHz
      • BOD : BOD 1.8V
      • EEPROM : EEPROM retained
      • Variant : 328P / 328PA
      • Bootloader : Yes (UART0)
    • only one open or closed contact on pin D3 with external pull-up of 1M ohm
    • radio is a RFM69HW
    • sketch is using the mysensors sleep function with interrupt wake up (MySensors lib version 2.3.2).

    To test if it was the radio module not completely sleeping and causing this consumption, I tested the same on a other pro mini (no power led and no power regulator, same refusing), without any external hardware, using the LowPower sketch from https://andreasrohner.at/posts/Electronics/How-to-modify-an-Arduino-Pro-Mini-clone-for-low-power-consumption/
    ==>same measurement : 133µA
    So the radio module is not the raison!

    So what is the cause of this higher consumption?
    The quality of the Chinese clone boards?
    Or is there still external hardware on the board consuming some current? The external crystal still present for example?

    Pro mini schematics.jpg

    On the pro mini, there is a led connected to the SCK pin. I think that will add an extra of +-1mA when the radio is active?
    But it has nothing to do with the sleep current of 133µA...

  • Mod

    @evb sorry for the late reply. I noticed your post earlier, but quickly realized I would need some time to catch up and grasp the full discussion. Now, when I finally have time to try to catch up, I realize that this is way beyond my capability of understanding. But if you provide instructions, I can paste them into the pages you deem relevant.

  • @mfalkvidd
    Ok, the first point is all about the image with the mention N/C
    (see https://forum.mysensors.org/topic/4796/battery-powered-sensors/232)
    We didn't know why this was set on the image.
    Now we do: there were or are pro mini's, if you desolder the voltage regulator, the mentioned VCC hole is not connected anymore.
    --> if you have a pro mini where this is the case, you can't use anymore the usb-to-ttl programmer like that because the pro mini won't be powered on anymore by the VCC of your programmer. You must connect the VCC pin of the programmer with a wire to the other VCC hole.
    --> in the other case, like mine pro mini version, no problem, the VCC hole at the right is still connected.

    The second point is all about the struggle to change/adapt/update existing site articles with updated/corrected/extended information 🙂
    I see that most site articles have the submenu 'Related Content'. In most articles this is empty. Can't we use that to link to forum topics with more information, I mean forum topics with a great deal of explanation or real world examples.
    So that the reader has directly more information to read on the subject, without to be obliged to read hundreds of forum topics before finding the ones with adequate information.
    For example I started with the pro mini, because mentioned in the site article, but today I'm aware that this was maybe not the way to go...
    An example of such a forum topic is : https://forum.mysensors.org/topic/2067/my-slim-2aa-battery-node.

  • Mod

    Thanks @evb. I have added the content:

    As for the related content, I am not aware of any way to affect that part. To my knowledge, each page links to its own forum thread. For the battery page, it links to the forum thread we are currently posting in.

  • Mod

    @evb said in 💬 Battery Powered Sensors:

    As far as the current of my pro mini is concerned, I'm stuck at a minimum of 133µA.

    So how low do you want to go? The original article mentions 120uA, so you seem to be pretty close to that value.

  • @Yveaux, after your comment, I did a search on '120' and you are right, it is even mentioned at the beginning of the article! 😲
    I think I was to focused on the table of the Radio Power Consumption and on the forum topic https://forum.mysensors.org/topic/2067/my-slim-2aa-battery-node with a sleep consumption of:
    The Sleep Mode Power Consumption
    I measured the sleep mode current draw to be 1.5uA when it's set to interrupt wake up and 5.8uA when it's set to timer wake up.

    So the 133 µA is indeed very close to the 120µA mentioned!
    So my node is functioning in the wanted consumption range, nothing wrong! 🙂

  • Mod

    one of the eternal problems with documentation: There is always something missing that should be added, but there is also always too much information for someone to read and comprehend.

  • Mod

    hek kindly explained to me how the related content works. Google generates it based on their magic. So that's why I was unable to find out how to affect it.

  • @mfalkvidd, thanks for searching this out 🙂
    So it is not really usable as a new section for linking adequate forum topics.

    Can we add then a new section called for example 'More (advanced) information' and put there more information for users wanting more (advanced) information? It can be extra text information or here for example a link to a advanced useful forum topic like I already mentioned.

    What do you think about it?
    My intention is to let others avoid the mistake I have made.
    If we can provide some targeted links to topics that go deeper on the (basic) content of the article, then that is a win-win situation. The user gets his information and new ideas faster and the topic starter gets recognition for his work 🙂
    As a user and certainly a beginner, it is sometimes overwhelming to search the forum and to distinguish useful topics from unusable ones.

  • Mod

    @evb yes, adding a new section is easy. I’ll add one when I’m not on mobile.

  • Mod

    New section added

  • Does enabled myDebug and some Serial.print statements (with serial port disconnected) affect power consumption of the node?

  • @APL2017 I have no hard evidence, but logically this will take a little more processor time, so a little more power consumption.
    But in my opinion, this is going to be negligible as long as you don't have thousands of lines with serial.print statements.

  • @APL2017 debug and serial print are for developmenat only. They will use more power and slow the system (node) down slightly.

    When things are working well, remove debug and serial print from your sketches.

  • Mod

    I keep my debug statements. If the node starts to act up, I want to be able to connect a logger and se what is happening without having to flash the node first.

  • If I remember correctly, writing to the serial port takes about 10s / baud rate for a single byte. That's a little unter 90µs at 115200 baud (common for Arduinos clocking 16 MHz at 5V) or about 1ms at 9600 baud (1MHz for 3V or less).

    Imagine we are transmitting two messages per wake cycle and print another few custom lines to the serial port as well, that may result in about 500 bytes total. This would then add another 45ms on a fast clocking Arduino (115200 baud) or 0.5s (9600 baud) - plus likely some overhead - to the time the microcontroller spends in an active state.

    According to the datasheet (p.312), an ATmega328P clocking at 1MHz consumes about 0.5mA in an active state at about 3V. So, from here on, you could calculate how drastically (or not) an additional ~0.1 - 0.7s of active time per wake cycle would impact the runtime of the battery.

    Since it's possible to run a node for a year or much longer off a set of batteries if it doesn't send lots of messages every few minutes, I doubt you would be able to notice a difference between disabling debug prints or keeping them.

    It is usually much more important to keep the current consumption during the power down phase as low as possible, than shedding off a few ms of active time.

  • @evb Hello. I am the maker of the Canique MK2 boards. I started just like you with the website from Andreas Rohner, desoldering the LED and desoldering the voltage regulator from such a chinese board until I realized this is the wrong way round.
    As far as I recall, I've seen voltage regulators consume something in the order of 100uA when reverse powered. So that might be a hint.
    The external crystal should not be drawing that much current. Using a 16MHz oscillator current can go as low as 4uA with watchdog enabled - in theory and on boards built with minimum consumption as a design goal.

    To your question regarding the SCK pin: yes, if it is connected to a LED every clock pulse on the SCK pin (when SPI is enabled) will make the LED draw current.

    You also have these kinds of troubles (SPI drawing too much current when active or inactive) with chinese boards having a BME280 on them for example. If you have high quality standards, the stock chinese boards won't fit your needs.

  • @evb little info regarding the LED on the SCK pin.
    Assuming it is a red LED with a forward voltage of 1.8V, considering the chip is powered with 3.3V and considering the 330 Ohm resistor in series with the LED, the additional current draw when SCK goes high should be about 4.5mA.

  • @canique you confirm my suspicions. For the moment I have 3 working battery nodes with the pro mini and the RFM69HW. We will see how long the batteries are going to last. Normally it should be one year.

    I'm constrained by the maximum dimensions of the sensor node. The case must go inside the PVC door frame, so it can be maximum 20mm width on 17mm height, the length is not a constraint. 🙂
    I had to solder the RFM69HW in line with the pro mini.
    The MK2 boards are unfortunately too wide.

  • Mod

    @evb how's the range of your node? Being enclosed in aluminum will definitely reduce range.

  • @evb I can't see it clearly on the picture but this seems like a reed sensor to me.
    Well, usually the transmitter does not have to be at some specific location. There are reed sensors based on magnets (connected with 2 wires to the transmitter). As soon as the magnets are close to each other, a small current flows (or vice versa). They are just attached to the window/door with some sticky adhesive. The transmitter can well be a meter away.

    I can say from experience with Atmega328P, that when drawing ~24uA in sleep and sending every 30 seconds a single battery lasts ~ 1 year.
    This can all be calculated (rough estimates).
    A basic online calculator for this kind of stuff can be found @ https://oregonembedded.com/batterycalc.htm

  • @Yveaux It is not a aluminium door frame, but a PVC door frame (plastic).
    The problem is that my gateway is in the extension of the brick wall, about 15m away in the garage at the backyard. So I have a 5m brick wall between de node and the gateway 😞
    This means that the reliability of the connection is not good, so I had to place a repeater node between them.

  • @canique no, the purpose of the node is to know when the door is locked by the bolt, not only closed. What you see are simply 2 battery springs and the bolt of the lock closes the contact.
    I can move the node more upwards the door frame (and I will do it if the radio connection is still not reliable with the repeater).
    In order to preserve domestic peace, I placed the nodes in the door frame, invisible when the door is closed: no visible dangling wires and no visible boxes.

    Maybe an idea for a MK3 version of your board as wide as the RFM69HW 😉

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